A plurality of regularly arranged yarns undergo knitting, weaving, take-up and other operations in the looms, knitting machines, warpers and other spinning and weaving machines, and when there takes place break of yarn(s) in such process, it needs to immediately stop the machine and to issue an alarm. If the knitting or weaving and/or take-up operations are allowed to proceed with even a single piece of yarn left broken, there would occur a knitting or weaving flaw or an incorrect mode of take-up, resulting in a serious degradation of the product quality. Also, the broken yarn end may wind round the machine elements to cause a damage thereto. In order to avoid this, various types of yarn break detectors have been proposed and used.
There are known, for instance, a mechanical detection system in which an actuator is attached to a microswitch with yarn let run in contact with said actuator so that, in the event of yarn break, said actuator will detect the loss of yarn tention and operates the microswitch to issue a yarn break signal, and an electronic detection system in which the run and stoppage of yarn are monitored by a photoelectric sensor comprising a light projector, or the yarn run signal is detected by the variation of electrostatic capacity.
However, these yarn break detectors, although adaptable to certain specific types of yarn and yarn arrangements, can not be applied to a machine in which a plurality of yarns are arranged closely to each other.
The yarn detectors of said mechanical system are appliable where the yarn count is large, the yarn running speed is low and the running yarn tention is high, but their scope of use is very limited.
Also, the yarn break detectors of said conventional electronic system, although well filling up the deficiencies of said mechanical system, are still unappliable to all of the yarns arranged at high density, for example, feed yarns in warping and knitting machines, warps in weaving machines, and yarns arranged closely to each other in such a large number as several hundred or more at an interval of about 1 millimeter, such as those placed close to the take-up beam in a warping machine.
This is due to the fact that it is quite difficult to construct the detecting section of the conventional electronic yarn break detectors as a unit of less than 1 millimeter in size, and even if it should be possible to construct said detecting section with a size of several millimeters and to widen the yarn interval, there then arises the problem of high production cost.
As a conventional yarn break detector for yarns arranged at high density, there is known a system in which a light beam is projected adjacent to the arrangement of yarns and should a yarn be broken such yarn hangs down and traverses said light beam, whereupon a signal is issued. This system, however, is still low in accuracy of detection and also subject to limitations in its location of installation.
The present invention has been made in view of said problems of the prior art and has for its object to provide a yarn break detector which is capable of accurately and quickly detecting break of yarns arranged at high density.
It is also an object of this invention to provide a yarn break detector which is small in size and hence not limited in its location of installtion and is also easy to handle and low in cost.